Rotating or sliding surfaces between moving parts of an engine are typically lubricated, with a lubricant such as motor oil. Lubrication systems may include an oil pump configured to circulate oil from an oil pan, or oil sump, and into a number of oil passages, or galleries to various locations in the engine to lubricate bearings supporting the camshaft(s), the crankshaft, connecting rods, and the like. Some rotating members, such as camshafts include an axial passage configured to receive oil, and a radial passage at one or more bearings to pass the oil to the rotating bearing surface. The oil may return to the oil pan for recirculation after splashing around the engine, and/or running down various parts of the engines.
Debris that may be in the oil, and/or that may accumulate from surface wear can grind against moving parts, causing additional wear. Therefore, in an attempt to remove potentially harmful particles the oil is first passed through an oil filter before being directed to the oil galleries, or to other parts of the engine. However, it has been recognized that despite filtering the oil before being passed to the galleries, and/or other parts, some particles can get into undesirable locations such as bearing surfaces.
It has been proposed to include additional filters in the lubrication system. For example, U.S. Pat. No. 6,343,580 discloses locating an additional replaceable filter element in an enlarged bore formed at an upper end of an oil gallery formed in the cylinder head which cooperates with a corresponding main oil gallery formed in the associated cylinder block. The gallery in the cylinder head is intersected by a pair of supply passages, which communicate with drillings formed in the intake and exhaust camshafts. The drillings intersect radial drillings formed in the bearings to supply oil to the bearing surfaces.
However, the inventors herein have recognized some problems with this approach, for example, the filter disclosed in the '580 patent is located substantially far upstream from the camshaft bearings, in particular from the bearing furthest from the supply passages in communication with the drillings in the camshafts. The inventors have identified engine failures due to camshaft seizure of the number one bearing journal which may be located at the end of a camshaft furthest from an oil entry point. Debris entrained in the oil may enter the journal bearing interface and may cause the camshaft to seize. What is needed is a more effective way to prevent debris from entering the journal bearing interface.
Embodiments in accordance with the present disclosure may provide a camshaft having a central oil passage and a radial passage to supply oil from the central passage to a bearing surface. The camshaft may include a filter disposed within the central passage which may allow oil to pass through the radial passage to the bearing surface, and which may prevent particles larger than a predetermined size to pass to the bearing surface. In this way by placing an oil filter internally in the camshaft, any debris passing down the center of the camshaft may be filtered out, resulting in a continuous supply of clean oil to the journal bearings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.